Paycheck / Take-Home Pay Estimator mechanism

Model scope

The catalog formula is not ready for an unqualified PASS. The main defects are the incomplete FICA statement, unspecified treatment of deduction types, and insufficient W-4/state inputs. The four vectors use 2024, single-filer, Texas, annualized educational assumptions and are intended as verification fixtures, not a substitute for the actual IRS or state withholding procedure.

• The stated FICA formula, "7.65% to cap," is incomplete and misleading: Social Security is 6.2% only up to the annual wage base, while Medicare is 1.45% with no wage cap; Additional Medicare Tax of 0.9% may apply above statutory thresholds.
• The formula subtracts pre-tax deductions after calculating withholding without specifying which deductions reduce federal income-tax wages, which reduce state wages, and which remain subject to FICA. Traditional 401(k) contributions generally reduce federal income-tax wages but remain subject to Social Security and Medicare; HSA treatment depends on payroll arrangement and jurisdiction.
• Federal withholding cannot be determined from gross pay and filing status alone. The IRS W-4 year, pay-period wages, Step 2 checkbox, dependents credit, other income, other adjustments, and extra withholding are missing.
• State withholding requires a year-dated state table and additional state-specific inputs. State alone is insufficient; some states require allowances, filing status distinctions, local taxes, or reciprocity information.
• The formula does not specify whether amounts are rounded per paycheck, whether annualized withholding is used, or how irregular pay, bonuses, multiple jobs, and wage-base tracking are handled.
• The test calculations below use a clearly stated educational annualized-tax convention for federal estimates. That convention is not identical to every employer's IRS percentage-method withholding calculation, so the instrument must not label these outputs as exact payroll withholding.

Units and conventions

• All monetary inputs and outputs are U.S. dollars for the stated pay period unless explicitly marked annual.
• The worked vectors use 2024 federal parameters: single-filer standard deduction of $14,600, 2024 single-filer tax brackets, Social Security rate 6.2%, Medicare rate 1.45%, and Social Security wage base $168,600.
• For the annualized examples, annual gross pay equals per-pay-period gross multiplied by the number of periods: 52 weekly, 26 biweekly, or 1 annual.
• Texas is used for every state example; state withholding is assumed to be zero because Texas has no individual state income tax.
• Traditional 401(k) deductions reduce federal income-tax wages but remain subject to Social Security and Medicare in the examples.
• Federal amounts for periodic examples are annualized federal income-tax estimates divided by the number of pay periods, with final results rounded to cents.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "gross_pay": 100,
    "pay_frequency": "weekly",
    "pay_periods_per_year": 52,
    "filing_status": "single",
    "state": "TX",
    "pre_tax_deductions": 0,
    "deduction_type": "none",
    "tax_year": 2024
  },
  "expected_outputs": {
    "federal_withholding": 0,
    "social_security": 6.2,
    "medicare": 1.45,
    "fica_total": 7.65,
    "state_withholding": 0,
    "pre_tax_deductions": 0,
    "estimated_net_pay": 92.35
  },
  "reference_data": {
    "federal_standard_deduction_single_2024": {
      "value": 14600,
      "source_convention": "IRS 2024 federal tax parameters"
    },
    "federal_single_bracket_0_to_11600": {
      "rate": 0.1,
      "source_convention": "IRS 2024 federal tax brackets"
    },
    "texas_individual_income_tax": {
      "value": 0,
      "source_convention": "Texas Comptroller statutory convention: Texas has no individual state income tax"
    },
    "social_security_rate": {
      "value": 0.062,
      "source_convention": "IRS/SSA 2024 payroll-tax convention"
    },
    "medicare_rate": {
      "value": 0.0145,
      "source_convention": "IRS/SSA 2024 payroll-tax convention"
    }
  },
  "working": "Annualized gross = $100 × 52 = $5,200. Annualized federal taxable income = max($5,200 − $14,600, 0) = $0, so federal withholding = $0. Social Security = $100 × 6.2% = $6.20. Medicare = $100 × 1.45% = $1.45. FICA = $6.20 + $1.45 = $7.65. Texas withholding = $0. Net pay = $100 − $0 − $7.65 − $0 − $0 = $92.35. The $7.65 result is the widely memorized combined employee FICA rate on wages below the Social Security cap."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The specified instrument cannot produce complete nonzero paycheck results without year-stamped federal and state lookup tables. It also has a definite undefined-result trap when the pay-period denominator is zero, and it has a convention-sensitive deduction sign that can change the result by $400 in the probe.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche7/tranche7-results.json
• BOUNDARY_HAZARD_CATALOG.json